For the mother, a son was a hard thing. First, the production, the baby will generally heavier than some of the secondly, when the son, the mother testosterone content will of course, the boy grew up to be more noisy than naughty girl, who is also the mother a headache. University of Sheffield (University ofSheffield) of Weier Pi Luma (Virpi Lummaa) Now in the past two hundred years after the Finnish church records confirmed: sons will shorten the life of the mother, with an average length of 34 weeks.
This year 33-year-old Weier Pi Luma Finland evolutionary biologists, with the help of genealogists, she consulted hundreds of historical information dossier and the microfiche decades ago, trying to figure out the evolution of human reproduction Impact. Historians, economists, sociologists have even used this method to study in their respective fields, and Luma is the first modern human being as an animal for biologists, but we the number of such animals which data were available.
Human data collection easier, after all, in respect for the record, we have a clear advantage. Luma said: "I always wanted to study primate breeding situation, but the information you want to collect wild chimpanzees too difficult, eventually I intend to study another primate, which is human." Luma of a recent term work is pre-modern Finnish Sami mothers for the study, because Saami reindeer herding known.
Study results show that the Sami people, birth mother of the sons, daughters birth mother of life than short, and this weight and testosterone levels baby related. Luma said that testosterone can compromise the immune system, affect health. A son of the mothers of epidemic diseases (such as tuberculosis) are particularly "son of the cost of" larger than daughters, but also because the boy would absorb more nutrients from the mother, this and other mammals (such as red deer) the research is also consistent. Of course, the boy would grow up not too busy to help his mother, like daughter. Recently, Luma and her colleagues found that sons have a negative impact on not only the mother of the brothers and sisters, too. If the front tire was a boy, then the next child born head will be relatively small, family members will be relatively small when they grow up and are more vulnerable to the disease to death. Even first-born boy died, the impact on children born after generation of the same, that is to say, such a negative impact on not by the direct interaction between fellow generated, including the interaction between the compatriots fought, fight and primogeniture (eldest brother could inherit all that is heritage) and the like. Therefore, Luma said: "brother is not a good thing, if the fifth child is a boy, was born the sixth will be worse."
This phenomenon is more evident in twins. For the 1734 - 1888 five towns Finnish twins born 754 data statistics, in twins found Luma female marriage rate 15% lower than the Shuangfeng child, children 25% chance, and the average ratio The latter two have fewer children. No matter how different social status and cultural factors, the result is the same. Even when the boy twins within 3 months after birth died, the girl was raised as an only child, the situation is still the same.
Luma speculated that this result is in the uterus caused by testosterone. Researchers in other animals (including rats and cows) have been observed in experiments of this hormone effect. Cows sometimes birth to twins, one of the cows sometimes congenital absence of reproductive capacity.
Whatever the reason how the above phenomenon, there is a fact that there is: the mother of twins born, the number of grandchildren woman 19% less than the same-sex twins born mother. Biological evolution seems to prefer the latter. Northwestern University (Northwestern University) anthropologist Christopher long Ze (ChristopherKuzawa) said that biological differences between men and women not only from the inherent differences in the chromosome, the role can also affect fertility among compatriots on evolution is important.
In this regard, Pennsylvania State University (PennsylvaniaState University), a biological anthropologist and geneticist Kenneth Weiss (KennethWeiss) commented that the results are somewhat puzzling. He pointed out: "Although twinning is genetic, but evolutionary selection does not favor it, because twinning is not common but some animals but often twin phenomenon." He added that although this may seem contradictory, but even if we observe the phenomenon is real, if too much emphasis on rationality may still cause errors.
Indeed, if these results will be used to explain the actual situation today, it would be very inappropriate. Thanks to effective birth control, adequate food and neonatal mortality, the evolution of the impact as they used to seem obvious. Luma said that 100 to 150 years ago, babies grow into adulthood (15 years old) in front, 40 percent will die, which today seems incredible.
But now the Finns before the world situation facing the majority of the population and industrialization, or the like. Luma said: "The more children born, spread to the next generation of the more genes, evolution or in principle always acting." She also wished to modern demographic information, test results she obtained from the Finnish people she is now located west coast of Africa to collect family health status recorded Gambia.
Meanwhile, Luma and her colleagues began to proceed from Finland Profile Another analysis - grandparents and evolutionary relationships. Early results show that, for grandmother grandson woman survived and fertility have a direct help, father and grandfather did not. Although his father alive child will get married earlier, but the number of grandchildren woman did not increase the effect. And traditional cultural might to men, especially men grandparents about the concept first, Luma said:. "If there was a negative impact, that is, perhaps the grandfather and grandson would snatch"
One possibility is that evolutionary selection determines the life of women, while male life expectancy is only a by- Another possibility is that male life can procreate, so they did not pay much attention to their children. Another study is ongoing research Luma male's ability to have offspring, although this is somewhat contradictory and Finns monogamy. Luma explained: "Men over 50 years old are still people willing to be his partner, and women of childbearing age had a few people interested on, and if men have been offspring, then age will give them what good is it ? '
Luma and her colleagues have also used these data to analyze the evolution of social class, we found the former rich than the poor have more children, but now it seems completely backwards over. Luma speculates that perhaps now we pay more attention to "quality" rather than the level of care so much about the number of "quantity", but the clear answer "yet to find."
Men "harmful" and the grandmother of "good" Obviously, this has just given birth to March this year, the son of Ellis (Eelis) of Luma is not good news. She laughed: "son takes a lot of effort, I was also getting old, those children born each year a woman is really amazing!"
Although the son of costly, but the son does not only harm. Luma said: "From an evolutionary point of view, if you gave birth to a son, real good, he'll give you a bunch of grandchildren born son may have to pay a lot, but will also get a lot of.."
(Author: David translation: Pingze Jun)
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